Psycho-Physiological Effects of a Peony-Viewing Program on Middle-Aged and Elderly Individuals at Different Phenological Stages

To address the question of whether the behavior of humans to view different phenological peony flowers has various effects on their physical and mental parameters, we investigated psycho-physiological responses of 74 participants (61.3 ± 10.78 years old) to environments of pre- and post-viewing tree peonies at four stages, including the exhibition leaf stage (ELS), initial bloom stage (IBS), full bloom stage (FBS), and terminal bloom stage (TBS). Physiological factors were examined using systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate (HR), fingertip pulse (FP), blood oxygen saturation (SpO2), and psychological evaluation, which was carried out using the Profile of Mood States (POMS) and State–Trait Anxiety Inventory (STAI). The results indicated that the SBP, DBP, HR, and FP levels of participants were significantly reduced after viewing tree peonies, whereas no remarkable alterations in SpO2 were found. The POMS scores of anger–hostility (A–H), fatigue–inertia (F–I), tension–anxiety (T–A), confusion–bewilderment (C–B), and depression–dejection (D–D) were significantly lower, but of vigor–activity (V–A) was higher post-viewing than pre-viewing. Furthermore, participants exhibited markedly decreased anxiety levels according to the STAI. Notably, the changes in measurement indices were more pronounced at the FBS. Our studies demonstrated that a short peony-viewing program, especially at the FBS with completely opened and large tree peony flowers, would be a promising therapeutic method for improving physiological functions as well as an effective psychological relaxation strategy for middle-aged and elderly individuals.


Introduction
Human beings have been inextricably linked to the natural environment [1]. A growing body of scientific evidence indicates that direct or indirect interaction with nature or plants is beneficial to human health and well-being [2][3][4][5]. Simultaneously, environments with natural elements can better relieve stress and mental fatigue than those without natural elements [6]. Since the 1970s, horticultural therapy has been developed rapidly in Europe, America, Japan, and other countries, mainly relying on medical instruments and psychological methods to study the effects of plants on human psycho-physiological health through two aspects of human sensory stimulation (vision, olfaction, touch, audition, and taste) and horticultural practice [7,8]. These studies have shown that plants and gardening have significant therapeutic effects on physical and mental health.

Participants
This study was performed with 74 middle-aged and elderly subjects aged 44 to 83 years (61.3 ± 10.78; mean ± SD), consisting mainly of faculty members and senior citizens with normal visual acuity and no history of neurological illness. None of the subjects had abnormalities affecting smell (e.g., pollen allergy, stronger/weaker senses of smell), and they were asked not to use any sprays or perfumes prior to the experiments [43]. The gender distribution of participants was 37 females (50%) and 37 males (50%). The participants' personal information and characteristics are listed in Table 1. A questionnaire [34] used to evaluate participants' health conditions before the test included the following questions: "Before the test, did you stay up late?", "Eight hours before the test, did you drink alcohol?", "Eight hours before the test, did you take any (antihypertensive) drugs?", and "eight hours before the test, did you have coffee or similar beverages?". These health factors may influence physiological testing and were used for exclusion criteria before the experiments. The participants answered all the questions during every experiment of each phenological stage of peony. In addition, the study was conducted in accordance with the ethics rules of Northwest A&F University.

Experimental Setting
The research was conducted in the peony garden ( Figure 1), which was surrounded by four roads. The peony garden had roads, seats, a rest square, and a number of tree peony cultivars. It was 215 m long (east-west) by 30 m wide (north-south) and covered an area of approximately 0.67 ha. The tree peonies were approximately 8-10 years old [44]. The height of the trees was 0.5 ± 0.1 m, and the number of blooms per tree was 18 ± 6. This study was conducted separately at the exhibition leaf stage (ELS), initial bloom stage (IBS), full bloom stage (FBS), and terminal bloom stage (TBS). The leaf buds of the whole tree were basically expanded at the exhibition leaf stage. Most peony petals were slightly opened, but a few had already opened and were at the initial bloom stage. The peony petals were all opened to the maximum extent at the full bloom stage. Most of the peony petals began to fade at the terminal bloom stage [44]. The morphological characteristics of peony flowers were shown in Figure 2. During the peony-viewing program, there was no rain and the weather was pleasant with a temperature of 22.7 ± 1.6 • C, a relative humidity of 54.3 ± 2.5%, and a wind speed of 1.5 ± 0.3 m/s. In addition, the roads around the peony garden were closed for traffic by the campus managers to keep a good environmental condition for the experiments. perfumes prior to the experiments [43]. The gender distribution of participants was 37 females (50%) and 37 males (50%). The participants' personal information and characteristics are listed in Table 1.
A questionnaire [34] used to evaluate participants' health conditions before the test included the following questions: "Before the test, did you stay up late?", "Eight hours before the test, did you drink alcohol?", "Eight hours before the test, did you take any (antihypertensive) drugs?", and "eight hours before the test, did you have coffee or similar beverages?". These health factors may influence physiological testing and were used for exclusion criteria before the experiments. The participants answered all the questions during every experiment of each phenological stage of peony. In addition, the study was conducted in accordance with the ethics rules of Northwest A&F University.

Experimental Setting
The research was conducted in the peony garden ( Figure 1), which was surrounded by four roads. The peony garden had roads, seats, a rest square, and a number of tree peony cultivars. It was 215 m long (east-west) by 30 m wide (north-south) and covered an area of approximately 0.67 ha. The tree peonies were approximately 8-10 years old [44]. The height of the trees was 0.5 ± 0.1 m, and the number of blooms per tree was 18 ± 6. This study was conducted separately at the exhibition leaf stage (ELS), initial bloom stage (IBS), full bloom stage (FBS), and terminal bloom stage (TBS). The leaf buds of the whole tree were basically expanded at the exhibition leaf stage. Most peony petals were slightly opened, but a few had already opened and were at the initial bloom stage. The peony petals were all opened to the maximum extent at the full bloom stage. Most of the peony petals began to fade at the terminal bloom stage [44]. The morphological characteristics of peony flowers were shown in Figure 2. During the peony-viewing program, there was no rain and the weather was pleasant with a temperature of 22.7 ± 1.6 °C , a relative humidity of 54.3 ± 2.5%, and a wind speed of 1.5 ± 0.3m/s. In addition, the roads around the peony garden were closed for traffic by the campus managers to keep a good environmental condition for the experiments.

Research Design
We adopted a one-group pretest-posttest field experimental design to evaluate the participants' physiological activity and mood states incurred by viewing tree peonies. Specifically, all participants' physiological and psychological responses were measured before they viewed tree peonies (baseline), and post-program measures were obtained upon their return. The effects of viewing tree peonies on physiological activity and mood states could therefore be identified by comparing the baseline and posttest measurements.
The experiments were conducted when the tree peonies were at the exhibition leaf stage (ELS), initial bloom stage (IBS), full bloom stage (FBS), and terminal bloom stage (TBS), severally, from 9:00 am to 12:00 pm on 2-27 April 2018. Four tests were carried out at each phenological stage, respectively ( Figure 3). The participants gathered at a designated location. Before the start of the experiment, the participants were allowed to move freely in the courtyard space (with hard pavement, a stone table, and several buildings, but without peonies ( Figure 1)) for 15 min [16]. Their pre-and post-psychophysiological indicators were recorded, and they were treated as a control group. Then, all participants took part in the experiment in a prearranged order and entered the peony garden to watch tree peonies. Their pre-and post-viewing physiological and psychological indicators were recorded. A guided 15-minute peony-viewing program was organized to include the major stimulation of two senses, namely, vision (e.g., peony leaves, flower colors) and olfaction (e.g., the volatiles of peonies). During this process, subjects were allowed to touch the tree peonies, but not to talk with others, look at the phone, and walk out of the peony garden. Each participant walked for approximately 300 meters in the peony garden. The specific steps are as follows ( Figure 2).

Research Design
We adopted a one-group pretest-posttest field experimental design to evaluate the participants' physiological activity and mood states incurred by viewing tree peonies. Specifically, all participants' physiological and psychological responses were measured before they viewed tree peonies (baseline), and post-program measures were obtained upon their return. The effects of viewing tree peonies on physiological activity and mood states could therefore be identified by comparing the baseline and posttest measurements.
The experiments were conducted when the tree peonies were at the exhibition leaf stage (ELS), initial bloom stage (IBS), full bloom stage (FBS), and terminal bloom stage (TBS), severally, from 9:00 am to 12:00 pm on 2-27 April 2018. Four tests were carried out at each phenological stage, respectively ( Figure 3). The participants gathered at a designated location. Before the start of the experiment, the participants were allowed to move freely in the courtyard space (with hard pavement, a stone table, and several buildings, but without peonies ( Figure 1)) for 15 min [16]. Their pre-and post-psycho-physiological indicators were recorded, and they were treated as a control group. Then, all participants took part in the experiment in a prearranged order and entered the peony garden to watch tree peonies. Their pre-and post-viewing physiological and psychological indicators were recorded. A guided 15-min peony-viewing program was organized to include the major stimulation of two senses, namely, vision (e.g., peony leaves, flower colors) and olfaction (e.g., the volatiles of peonies). During this process, subjects were allowed to touch the tree peonies, but not to talk with others, look at the phone, and walk out of the peony garden. Each participant walked for approximately 300 m in the peony garden. The specific steps are as follows ( Figure 2).

Research Design
We adopted a one-group pretest-posttest field experimental design to evaluate the participants' physiological activity and mood states incurred by viewing tree peonies. Specifically, all participants' physiological and psychological responses were measured before they viewed tree peonies (baseline), and post-program measures were obtained upon their return. The effects of viewing tree peonies on physiological activity and mood states could therefore be identified by comparing the baseline and posttest measurements.
The experiments were conducted when the tree peonies were at the exhibition leaf stage (ELS), initial bloom stage (IBS), full bloom stage (FBS), and terminal bloom stage (TBS), severally, from 9:00 am to 12:00 pm on 2-27 April 2018. Four tests were carried out at each phenological stage, respectively ( Figure 3). The participants gathered at a designated location. Before the start of the experiment, the participants were allowed to move freely in the courtyard space (with hard pavement, a stone table, and several buildings, but without peonies ( Figure 1)) for 15 min [16]. Their pre-and post-psychophysiological indicators were recorded, and they were treated as a control group. Then, all participants took part in the experiment in a prearranged order and entered the peony garden to watch tree peonies. Their pre-and post-viewing physiological and psychological indicators were recorded. A guided 15-minute peony-viewing program was organized to include the major stimulation of two senses, namely, vision (e.g., peony leaves, flower colors) and olfaction (e.g., the volatiles of peonies). During this process, subjects were allowed to touch the tree peonies, but not to talk with others, look at the phone, and walk out of the peony garden. Each participant walked for approximately 300 meters in the peony garden. The specific steps are as follows (Figure 2).

Physiological Indices
A biofeedback measurement method was used as previously described [28], based on a variety of advanced electronic instruments to display the body's internal physiological activities stimulated by the visual or auditory signals. This method has been widely used in the field of people-plant relationships to examine the changes of physiological conditions of subjects. In our study, participants' systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate (HR) were measured by sphygmomanometer (Omron, HEM-7136, Kyoto, Japan) [42]. A fingertip pulse oximeter (M70C) was used to record the fingertip pulse (FP) [32] and blood oxygen saturation (SpO 2 ) [45].
Blood pressure and HR are the most commonly used indicators to detect the health status of the cardiovascular system, reflecting the activity of the human autonomic nervous system including the sympathetic nervous system (SNS) and the parasympathetic nervous system (PNS) [32]. In general, the SNS is associated with accelerated HR and increased blood pressure, and the PNS is associated with slower HR and lower blood pressure. An increased HR in humans represents an increase in the degree of tension and physiological arousal.

Psychological Indices
A psychological test method [46] was employed to observe the psychological and social phenomena of groups or individuals using a specific psychological rating scale and to quantitatively evaluate and explain the results. In this experiment, two psychological scales, the State-Trait Anxiety Inventory (STAI) [28] and the Profile of Mood States (POMS) [37], were used to test subjects' psychological conditions. The STAI questionnaire was composed of 20 questions, each with a score of 1-4 points. Participants' state-anxiety scores were determined by summing up their ratings of the 20 questions (e.g., I feel comfortable; I feel confused; I am satisfied). Higher scores indicated higher anxiety levels. The POMS questionnaire consisted of 35 questions and was divided into 6 dimensions: anger-hostility (A-H), depression-dejection (D-D), tension-anxiety (T-A), confusion-bewilderment (C-B), vigor-activity (V-A), and fatigue-inertia (F-I). A higher score for each dimension indicated a higher degree of the specified emotion.

Data Analysis
Data were analyzed by SPSS 19.0 (IBM ® SPSS ® Statistics, Armonk, NY, USA). A paired sample t-test was used to compare the means for psycho-physiological data in all experimental groups and control groups. The psycho-physiological changes between the experimental groups at different stages were determined by one-way analysis of variance (ANOVA). Partial eta squared (η p 2 ) was used to report the estimate of effect sized for the ANOVA. The data were expressed as the mean ± standard deviation (mean ± SD). In all comparisons, a p-value of <0.05 was considered statistically significant. Effect size was reported using Cohen's d.

Results
Results of the paired samples t-test indicated that there were significant differences in the systolic blood pressure (SBP) (p < 0.01 for all stages, with Cohen's d varying from 0.21 to 0.45), diastolic blood pressure (DBP) (p < 0.01 for all stages, d = 0.24-0.51), heart rate (HR) (p < 0.05 for all stages, d = 0.20-0.37), and fingertip pulse (FP) (p < 0.05 for all stages, d = 0.18-0.28) of middle-aged and elderly people in the test groups relative to the control groups in the four periods. However, the SpO 2 (p > 0.05) showed no significant differences ( Figure 4, Table 2). Compared with the other three periods, the changes in the SBP (p = 0.00, d = 0. Furthermore, there were no significant alterations in the SBP, DBP, HR, and FP between the IBS and the FBS. The changes in DBP and FP between the initial bloom stage (IBS) and the terminal bloom stage (TBS) were not significant after participants viewed tree peonies, and the changes of FP caused by initial bloom stage (IBS) and exhibition leaf stage (ELS) were not significant ( Figure 5). stage (TBS) were not significant after participants viewed tree peonies, and the changes of FP caused by initial bloom stage (IBS) and exhibition leaf stage (ELS) were not significant ( Figure 5).    (Figures 6A and 7, Table 3). The changes of the POMS and STAI scores were significant (p < 0.01) among the experimental groups. One-way analysis of variance revealed that viewing the tree peonies in the four periods reduced anxiety (p = 0.00, η p 2 = 0.29), A-H (p = 0.00,  Figures 6B and 8).    0.24), F-I (p = 0.00, ηp 2 = 0.24), D-D (p = 0.04, ηp 2 = 0.06), T-A (p = 0.00, ηp 2 = 0.06), and C-B (p = 0.00, ηp 2 = 0.07), and it beneficially affected V-A (p = 0.00, ηp 2 = 0.35). In addition, there were no significant differences in the anxiety of STAI scores between IBS and FBS. The changes between initial bloom stage (IBS) and exhibition leaf stage (ELS) in A-H, D-D, and C-B of POMS scores were not significant after participants viewed tree peonies, and the changes of T-A, C-B, and V-A caused by initial bloom stage (IBS) and terminal bloom stage (TBS) were not significant ( Figure 6B and Figure 8).

Discussion
This study explored the physiological and psychological responses of middle-aged and elderly individuals to tree peonies. Compared to the measurements for the control groups, physiological parameters (SBP, DBP, HR, and FP) and POMS (A-H, D-D, T-A, C-B, F-I, and V-A) and STAI scores were determined to have changed significantly after the peony-viewing program in each period, especially in the FBS. These outcomes, showing that visual interaction with nature or plants could relax people and reduce stress, were similar to those found in previous studies [11][12][13][14][15][16][17][18][24][25][26]34,36,47]. However, our results suggest that the differences in SpO 2 levels were not significant after viewing tree peonies. SpO 2 is a relative measurement index of the amount of oxygen dissolved or carried in the blood. It indicates whether a person has a sufficient supply of oxygen and reflects the level of cardiorespiratory health [45]. SpO 2 can be determined by a pulse oximeter, which is often attached to the finger for measurement purposes. It remains unclear why SpO 2 did not change significantly in our study. It might be simply that the peony-viewing activity had limited effects on SpO 2 . Alternatively, this research may be unlike previous studies in which SpO 2 was evaluated under different medical situations (anesthesia, sleep apnea, and parturition) [48] in contrast to the green garden environment in this study.
It is worth mentioning that our research, differing from the previous studies, has been completed in different phenological periods of the tree peonies. With the opening of peony flowers, the morphology and aroma concentration of peony flowers are constantly changing. From the perspective of plant landscape, we consider that the present study suggested two key findings. First, the changes of psycho-physiological parameters were greatest at the full blooming stage. This indicated that rich landscape structures (complex flower types, big flowers, and various colors) could provide a more relaxed environment. Second, the aroma released from the peony flowers may form a smellscape [49]. The peony smellscape may lead to people's emotional relaxation, as previously described [50]. Therefore, we will explore the influence of peony flower types, colors, and volatile organic compounds on human health in future studies. The information can greatly contribute to the development of color therapy and aromatherapy with tree peonies. On this basis, we suggest that landscape architects properly and reasonably increase the application of tree peonies in the designs of landscape (e.g., the designs of parterres and flower borders) to create an aesthetic and health-promoting environment.
The present findings provided scientific evidence on the positive psycho-physiological benefits of peony-viewing to middle-aged and elderly individuals by investigating a small sample size in a campus environment, not a large sample size in a natural environment [16,17,26]. However, the tree peony flowering period lasts usually only 15 to 20 days. Thus, people cannot view peony flowers all year round. We should enrich the scenery of the peony garden by planting fall foliage plants to make up for the depressed landscape after the peony flowers fade. Because the great effects revealed in this study may be due to the compositions of different colors, fall foliage may have similar effects due to the contrast of colors, which may need a further study. We also request that the university consider increasing the availability of peony gardening operation activities in the peony garden, such as planting, weeding, watering, fertilizing, pruning, and harvesting. Peony-based activities provide opportunities for social interaction between middle-aged and elderly people, further contributing to their mental health improvement. In addition, we consider that the horticulturist can cultivate the tree peonies by forcing or retarding culture and make peony flowers bloom in all seasons besides the spring.
We must admit that the present study does have a few limitations, however. First, each participant visited the tree peonies only once for a short time, so that the differences of the data at different times (morning or afternoon) of day and the long-term effects on participants still remain unclear. Second, the lack of participants' personal information of confounding variables such as socioeconomic status, cultural background (e.g., peony culture researcher), group characteristic (e.g., hypertension, diabetes, heart disease, etc.), and personality (e.g., peony lover) potentially affects the accuracy and reliability of the experimental results. Additionally, the present study only used blood pressure, heart rate, blood oxygen saturation, and fingertip pulse to demonstrate the internal state of participants. Future studies should include the assessment of other physiological indices, such as brain activity, eye tracking, electrical conductivity of the skin, and salivary cortisol.

Conclusions
Our study revealed that the short peony-viewing program elicited a significant change in physiological and psychological indicators of middle-aged and elderly individuals among various experimental groups. However, no significant changes in SpO 2 occurred. Simultaneously, we found that the promotional effects of the peony-viewing program on the subjects' physical and mental health, in sequence, were FBS > IBS > ELS and TBS. We thus concluded that middle-aged and elderly people could substantially benefit from short peony-viewing programs in terms of body and mind.